In motor vehicle repair shops, one task often performed is the repair or replacement of a vehicle's transmission. The transmission is typically both heavy and awkward to lift. Typically an overhead hoist or winch is used to lift a transmission using chains or other lifting straps placed around the transmission body. However, in some repair shops called upon to remove a transmission from a vehicle, such a hoist is unavailable.
When no hoist is available, a hydraulic transmission jack is at times used to lower a transmission from the vehicle that may be raised above the floor on a lift. This is an intricate procedure because transmission jacks rarely interface well with the body of a typical transmission and the transmission is often balanced precariously on the jack. Transmissions typically have components such as control arms protruding from their bodies—components that could easily be damaged if the transmission were to fall off the jack. In addition, typical hydraulic floor jacks are prone to rolling on the floor and must be stabilized, typically by a person.
To remove (or install) a transmission typically requires at least three persons to safely accomplish the removal or installation. Three people may not be available when it is time to remove or install a transmission so a repair job may be stalled until additional help is available. Even if other mechanics are available, they must typically be pulled from whatever repair job they are performing thereby extending the time required to complete those jobs. Finally, because of the shape and weight of a typical motor vehicle transmission, raising or lowering the transmission imposes less than ideal body mechanics on the mechanic or other person involved. This situation often leads to back strain or other back injuries.